Evolution of Tank Material Temperatures during the Hydrogen Fueling Process

The existing hydrogen fueling protocols have been developed considering that measured gas temperatures should never exceed 85 °C, in an effort to protect the liner of Type 4 tanks from damage. This consideration results in overly conservative fueling protocols, as current industry standards for hydrogen fuel tanks allow for transient gas temperatures that exceed 85 °C, provided that the tank materials do not exceed this limit.

We studied the gas temperature development in a Heavy Duty (HD) Type 4 tank and its effect on tank material temperatures. The objective was to show that transient gas temperatures that temporarily exceed 85°C will not always result in overtemperature of the tank materials. We developed a Computational Fluid Dynamics (CFD) model of the fueling process and validated it using experimental data. The CFD model was used to determine heat transfer coefficient correlations between the gas and the liner. These heat transfer coefficient correlations were used in a 1D thermodynamic model of the vessel, which estimated the gas and tank wall temperatures during refueling. Simulations of the 1D model have shown that measured gas temperatures exceeding 85 °C do not necessarily result in liner overtemperature.

This study supports the recognition in standards and regulations that transient gas temperatures that exceed 85 °C at the end of fueling do not affect the vessel qualification requirements, and hence tank gas temperature sensors are not required to be identified as “safety critical” components for the purposes of the fueling protocol.